A semiconductor optical integrated device in which a plurality of semiconductor optical devices are integrated onto a single substrate is effective in optical fiber communication from the viewpoint of miniaturization of an optical module.
A butt joint (BJ) growth method has traditionally been known as one of techniques for integrating a plurality of semiconductor optical devices onto a single substrate in this way. With the BJ growth method one semiconductor optical device structure is made to grow on a substrate. After that, a portion of the semiconductor optical device structure is removed and another semiconductor optical device structure is made to selectively regrow in the portion.    Japanese Laid-open Patent Publication No. 2002-314192    Japanese Laid-open Patent Publication No. 2008-053501    Japanese Laid-open Patent Publication No. 2002-217446    Japanese Laid-open Patent Publication No. 2001-189523    Japanese Laid-open Patent Publication No. 2007-201072    Japanese Laid-open Patent Publication No. 2004-273993    Japanese Laid-open Patent Publication No. 2002-324936    Japanese Laid-open Patent Publication No. 2002-243946    Japanese Laid-open Patent Publication No. 2003-174224
The advantage of the above BJ growth method is that semiconductor optical devices can be designed independently of one another. With a semiconductor optical integrated device fabricated by the use of the BJ growth method, however, a crystal defect or abnormal growth which appears in a junction (BJ portion) between semiconductor optical devices may cause, for example, deterioration in the reliability or initial characteristics of the semiconductor optical integrated device.